Ideally, a surround sound playback system producing acoustic signals from a multi-channel audio source to a listening area should have loudspeakers positioned at all corners of the listening area to correspond with the designated position of each audio channel with a specific direction output of the multi-channel audio source. For instance, a 5.1 channel audio source has a front left audio channel, front right audio channel, a centre audio channel, a rear left audio channel, a rear right audio channel and a low frequency effects audio channel, the listening area should have 6 loudspeakers including a subwoofer located at the designated front left, front right, centre, rear left and rear right audio channel locations. The position of the subwoofer is preferably at the front of the listening area, centrally located and placed close to a wall.
In reality, it is inconvenient and difficult to position loudspeakers according to the designated position of the audio channels of a multi-channel audio source. Usually the mains powering the loudspeakers are located at the front of the listening area and wiring to connect up the rear loudspeakers is a problem. A solution to this problem is to use only front located speakers. However, this introduces another problem, which is the lack of surround sound effects, in particular, the lack of acoustic signals from the rear.
Audio systems attempting to provide surround sound effects using front located loudspeakers do exist. They typically make use of Digital Signal Processors to execute complicated algorithms to produce virtualised rear surround sound effects, which can be costly. Without using Digital Signal Processors, such audio systems are generally complex and difficult to implement. Furthermore, using Digital Signal Processors or not, such conventional audio systems generally produce sharp and narrow sound images, as illustrated in FIG. 1A, which undesirably restrict the area in which surround sound effects produced could be experienced.
A need therefore exists to provide a method and audio system for processing multi-channel audio signals for surround sound production on a plurality of loudspeakers to a listening area that addresses at least the above-mentioned problems.